for Ka = 1:5000
    LT = [1 1020 20000 5000*Ka];
    R = roots(LT);
    hold on
    plot (real(R(1)),imag(R(1)),'r*')
    hold on
    plot (real(R(2)),imag(R(2)),'bo')
    hold on
    plot (real(R(3)),imag(R(3)),'go')
end

